Allostatic Load as a Complex Clinical Construct: A Case-Based Computational Modeling Approach

Association of allostatic load with overall survival in epithelial ovarian cancer

OBJECTIVE

Elevated allostatic load (AL), an integrated, cumulative marker of physiologic damage due to socioenvironmental stress, is associated with increased mortality in patients with breast, lung, and other cancers. The relationship between allostatic load and mortality in ovarian cancer patients remains unknown. We examined the relationship between allostatic load and overall survival in ovarian cancer patients.

METHODS

This cross-sectional study used data from 201 patients enrolled in a prospective observational ovarian cancer cohort study at a National Cancer Institute-designated Comprehensive Cancer Center from October 2012 through June 2022. All patients underwent debulking surgery and completed a full course of standard-of-care platinum-based chemotherapy. Follow-up was completed through January 2024. Allostatic load was calculated as a summary score by assigning one point to the worst sample quartile for each of ten biomarkers measured within 45 days before the ovarian cancer diagnosis. High allostatic load was defined as having an allostatic load in the top quartile of the summary score. A Cox proportional hazard model with robust variance tested the association between allostatic load and overall survival.

RESULTS

There were no associations between allostatic load and ovarian cancer clinical characteristics. After accounting for demographic, clinical, and treatment factors, high allostatic load was associated with a significant increase in mortality (hazard ratio 2.17 [95%CI, 1.13-4.15]; P = 0.02).

CONCLUSION

Higher allostatic load is associated with worse survival among ovarian cancer patients. Allostatic load could help identify patients at risk for poorer outcomes who may benefit from greater socioenvironmental support during treatment.

Allostatic Load in Childhood, Adolescence, and Young Adulthood: Are Assumptions of Measurement Invariance Warranted?

OVERVIEW

Allostatic load represents the cumulative toll of chronic mobilization of the body's stress response systems, as indexed by biomarkers. Higher levels of stress and disadvantage predict higher levels of allostatic load, which, in turn, predict poorer physical and mental health outcomes. To maximize the efficacy of prevention efforts, screening for stress- and disadvantage-associated health conditions must occur before middle age-that is, during childhood, adolescence, and young adulthood. However, this requires that models of allostatic load display properties of measurement invariance across age groups. Because most research on allostatic load has featured older adults, it is unclear if these requirements can be met.

METHODS

To address this question, we fit a series of exploratory and confirmatory analytic models to data on eight biomarkers using a nationally representative sample of N = 4260 children, adolescents, and young adults drawn from the National Health and Nutrition Examination Survey dataset.

RESULTS

Exploratory and confirmatory models indicated that, consistent with allostatic load theory, a unidimensional model was a good fit to the data. However, this model did not display properties of measurement invariance; post-hoc analyses suggested that the biomarkers included in the final confirmatory model were most strongly intercorrelated among young adults and most weakly intercorrelated among adolescents.

CONCLUSIONS

These results underscore the importance of testing assumptions about measurement invariance in allostatic load before drawing substantive conclusions about stress, disadvantage, and health by directly comparing levels of allostatic load across different stages of development, while underscoring the need to expand investigations of measurement invariance to samples of longitudinal data.

Parameters of Hemodynamic Allostasis in Patients of Various Age Groups with Essential Arterial Hypertension

We determined the criteria for the diagnosis of hemodynamic allostasis and compared it with the index of allostatic load in patients of different age group with essential arterial hypertension without metabolic syndrome. The study included 87 subjects divided into 3 groups: patients with essential arterial hypertension at the age ⩽60 years (n=31; group 1), patients with essential arterial hypertension above 60 years (n=41; group 2), and healthy volunteers (n=15; age 25-69 years, group 3). The data of 24-h BP monitoring were processed by methods of linear and nonlinear rhythm analysis. Based on the analysis, parameters were identified that allow determining the state of allostatic regulation of the 24-h dynamics of BP, as well as parameters that determine the allostatic hemodynamic load on the cardiovascular system. The data obtained were compared with the index of allostatic load in patients of both groups. Regulation of the hemodynamics in patients with essential hypertension without metabolic syndrome in both age groups remained within the limits of hemodynamic allostasis forming the allostatic load on the body, which does not depend on patient's age.

Association of Allostatic Load With Overall Mortality Among Patients With Metastatic Non-Small Cell Lung Cancer

Importance

Adverse social determinants of health (SDHs) (eg, poverty) are associated with poor oncologic outcomes among patients with lung cancer. However, no studies have evaluated biological correlates of adverse SDHs, operationalized as allostatic load (AL), with mortality due to lung cancer.

Objective

To examine the association among AL, SDHs, and mortality among patients with metastatic non-small cell lung cancer (NSCLC).

Design, Setting, and Participants

This cross-sectional study of an observational cohort was performed at a National Cancer Institute-designated comprehensive cancer center with data accrued from June 1, 2017, to August 31, 2019. Patients with metastatic (stage IV) NSCLC enrolled at diagnosis into a prospective observational cohort study were included in the present analysis if they had all the biomarkers to calculate an AL score (N = 143). Follow-up was completed on August 31, 2021, and data were analyzed from July 1 to September 30, 2021.

Exposures

Social determinants of health.

Main Outcomes and Measures

Overall mortality and AL.

Results

A total of 143 patients met the study criteria with a median age of 63 (IQR, 55-71) years (89 men [62.2%] and 54 women [37.8%]). In terms of race and ethnicity, 1 patient (0.7%) was Asian, 7 (4.9%) were Black, 117 (81.8%) were White, 17 (11.9%) were of multiple races, and 1 (0.7%) was of other race or ethnicity. The mean (SD) AL was 2.90 (1.37). Elevated AL covaried with lower educational level (r = -0.26; P = .002), male sex (r = 0.19; P = .02), limited mobility (r = 0.19; P = .04), worsening self-care (r = 0.30; P < .001), problems engaging in usual activities (r = 0.21; P = .01), depressive symptoms (r = 0.23; P = .005), and a high number of stressful life events (r = 0.30; P < .001). Multivariable analysis found only increasing difficulty with mobility (r = 0.37 [95% CI, 0.13-0.60]; P = .002) and male sex (r = 0.63 [95% CI, 0.19-1.08]; P = .005) associated with higher AL. On adjusted analysis, elevated AL (hazard ratio, 1.43 [95% CI, 1.16-1.79]; P = .001) and low educational level (hazard ratio, 2.11 [95% CI, 1.03-4.34]; P = .04) were associated with worse overall mortality.

Conclusions and Relevance

The findings of this cross-sectional study suggest that higher AL was associated with adverse SDHs and worse overall mortality among patients with advanced NSCLC. These results provide a framework for replication and further studies of AL as a biological correlate for SDH and future prognostic marker.

Allostatic load in the context of disasters

Environmental disasters, pandemics, and other major traumatic events such as the Covid-19 pandemic or war contribute to psychosocial stress which manifests in a wide range of mental and physical consequences. The increasing frequency and severity of such events suggest that the adverse effects of toxic stress are likely to become more widespread and pervasive in the future. The allostatic load (AL) model has important elements that lend themselves well for identifying adverse health effects of disasters. Here we examine several articulations of AL from the standpoint of using AL to gauge short- and long-term health effects of disasters and to provide predictive capacity that would enable mitigation or prevention of some disaster-related health consequences. We developed a transdisciplinary framework combining indices of psychosocial AL and physiological AL to produce a robust estimate of overall AL in people affected by disasters and other traumatic events. In conclusion, we urge researchers to consider the potential of using AL as a component in a proposed disaster-oriented human health observing system.

Comparing different operationalizations of allostatic load measured in mid-life and their patterning by race and cumulative life course socioeconomic status

Since its conceptualization, there has been a lack of consensus on the best way to operationalize allostatic load (AL). As a marker of the cumulative, physiological wear and tear on the body resulting from chronic exposure to stressors, it follows that AL should be higher among people who have faced more stressful life experiences. Thus, the purpose of this study was to construct AL scores using different operationalizations and, as a measure of construct validity, compare whether each construction produced expected disparities in AL by race and a composite socioeconomic status (SES) variable which accounts for measures over the life course; we also explored differences by sex. We conducted the study in a sample of 45-52-year-old offspring from the Child Health and Development Studies, a longitudinal birth cohort established in the early 1960s. AL scores were constructed in 6 different ways and included 10 biomarkers from inflammatory, neuroendocrine, cardiovascular, and metabolic systems. Our main approach to constructing AL was to sum across high-risk biomarker quartiles, correct for medication use, and use sex-specific high-risk quartiles for specific biomarkers. Alternative constructions did not use sex-specific quartiles and/or weighted biomarkers within subsystems and/or did not correct for medication use. We estimated differences in AL scores by race, SES, sex and their pairwise interactions. All constructions of AL, including the main approach, produced expected disparities by race (higher scores for Black vs. non-Black participants) and life course SES (higher scores for low vs. high SES participants). However, disparities by sex only emerged when the AL score was constructed via approaches that did not use sex-specific high-risk quartiles; for these alternative constructions, overall, female participants had higher AL scores than male participants and Black female participants had the highest AL scores in the sample. For most constructions, the pairwise interaction between sex and SES, showed a stronger disparity in AL scores between low and high-SES female compared with low- and high-SES male participants; this suggests that, in terms of lowering AL, high life course SES may be more important for female than male participants. In conclusion, our results suggest that the basic AL concept is consistently expressed in different operationalizations, making it an especially useful and robust tool for understanding disparities by race and SES.

Allostatic Load and Its Impact on Health: A Systematic Review

INTRODUCTION

Allostatic load refers to the cumulative burden of chronic stress and life events. It involves the interaction of different physiological systems at varying degrees of activity. When environmental challenges exceed the individual ability to cope, then allostatic overload ensues. Allostatic load is identified by the use of biomarkers and clinical criteria.

OBJECTIVE

To summarize the current knowledge on allostatic load and overload and its clinical implications based on a systematic review of the literature.

METHODS

PubMed, PsycINFO, Web of Science, and the Cochrane Library were searched from inception to December 2019. A manual search of the literature was also performed, and reference lists of the retrieved articles were examined.We considered only studies in which allostatic load or overload were adequately described and assessed in either clinical or non-clinical adult populations.

RESULTS

A total of 267 original investigations were included. They encompassed general population studies, as well as clinical studies on consequences of allostatic load/overload on both physical and mental health across a variety of settings.

CONCLUSIONS

The findings indicate that allostatic load and overload are associated with poorer health outcomes. Assessment of allostatic load provides support to the understanding of psychosocial determinants of health and lifestyle medicine. An integrated approach that includes both biological markers and clinimetric criteria is recommended.

Towards integrated modeling of the long-term impacts of oil spills

Although great progress has been made to advance the scientific understanding of oil spills, tools for integrated assessment modeling of the long-term impacts on ecosystems, socioeconomics and human health are lacking. The objective of this study was to develop a conceptual framework that could be used to answer stakeholder questions about oil spill impacts and to identify knowledge gaps and future integration priorities. The framework was initially separated into four knowledge domains (ocean environment, biological ecosystems, socioeconomics, and human health) whose interactions were explored by gathering stakeholder questions through public engagement, assimilating expert input about existing models, and consolidating information through a system dynamics approach. This synthesis resulted in a causal loop diagram from which the interconnectivity of the system could be visualized. Results of this analysis indicate that the system naturally separates into two tiers, ocean environment and biological ecosystems versus socioeconomics and human health. As a result, ocean environment and ecosystem models could be used to provide input to explore human health and socioeconomic variables in hypothetical scenarios. At decadal-plus time scales, the analysis emphasized that human domains influence the natural domains through changes in oil-spill related laws and regulations. Although data gaps were identified in all four model domains, the socioeconomics and human health domains are the least established. Considerable future work is needed to address research gaps and to create fully coupled quantitative integrative assessment models that can be used in strategic decision-making that will optimize recoveries from future large oil spills.

Allostatic Load in Cancer: A Systematic Review and Mini Meta-Analysis

BACKGROUND

Individuals with cancer experience stress throughout the cancer trajectory. Allostatic load (AL), a cumulative multi-system measure, may have a greater value in stress assessment and the associated biological burden than individual biomarkers. A better understanding of the use of AL and its operationalization in cancer could aid in early detection and prevention or alleviation of AL in this population.

PURPOSE

To consolidate findings on the operationalization, antecedents, and outcomes of AL in cancer.

METHODS

Seven databases (CINAHL, Ovid MEDLINE, Web of Science, APA PsycInfo, Scopus, Embase, and Cochrane CENTRAL) were searched for articles published through April 2020. The NIH tools were used to assess study quality.

RESULTS

Twelve studies met inclusion criteria for this review. Although variability existed in the estimation of AL, biomarkers of cardiovascular, metabolic, and immune systems were mostly used. Associations of AL with cancer-specific variables were examined mostly utilizing population-databases. Significant associations of AL with variables such as cancer-related stress, positive cancer history, post traumatic growth, resilience, tumor pathology, and cancer-specific mortality were found. Mini meta-analysis found that a one-unit increase in AL was associated with a 9% increased risk of cancer-specific mortality.

CONCLUSION

This review reveals heterogeneity in operationalization of AL in cancer research and lack of clarity regarding causal direction between AL and cancer. Nevertheless, AL holds a significant promise in cancer research and practice. AL could be included as a screening tool for high-risk individuals or a health outcome in cancer. Optimal standardized approaches to measure AL would improve its clinical utility.

Aging and Allostasis: Using Bayesian Network Analytics to Explore and Evaluate Allostatic Markers in the Context of Aging

Allostatic load reflects the cumulative strain on organic functions that may gradually evolve into overt disease. Our aim was to evaluate the allostatic parameters in the context of aging, and identify the parameters that may be suitable for an allostatic load index for elderly people (>60 years). From previously published studies, 11 allostatic (bio)markers could be identified that sustain sufficient variability with aging to capture meaningful changes in health status. Based on reported statistics (prevalence of a biomarker and its associated outcome, and/or an odds/risk ratio relating these two), seven of these could be adopted in a Bayesian Belief Network (BBN), providing the probability of “disturbed” allostasis in any given elder. Additional statistical analyses showed that changes in IL-6 and BMI contributed the most to a “disturbed” allostasis, indicating their prognostic potential in relation to deteriorating health in otherwise generally healthy elderly. In this way, and despite the natural decline in variance that irrevocably alters the prognostic relevance of most allostatic (bio)markers with aging, it appeared possible to outline an allostatic load index specifically for the elderly. The allostatic parameters here identified might consequently be considered a useful basis for future quantitative modelling in the context of (healthy) aging.

Multi-Systemic Biological Risk and Cancer Mortality: The NHANES III Study

Multi-systemic biological risk (MSBR), a proxy for allostatic load, is a composite index of biomarkers representing dysregulation due to responses to chronic stress. This study examined the association of an MSBR index with cancer mortality. The sample included n = 13,628 adults aged 20–90 from the NHANES III Linked Mortality File (1988–1994). The MSBR index included autonomic (pulse rate, blood pressure), metabolic (HOMA_ir, triglycerides, waist circumference), and immune (white blood cell count, C-reactive protein) markers. We fit Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CI) of overall cancer mortality risk, according to quartiles (q) of the index. In multivariable models, compared to those in q1, q4 had a 64% increased risk for cancer mortality (HR = 1.64, 95% CI:1.13–2.40). The immune domain drove the association (HR per unit = 1.19, 95% CI:1.07–1.32). In stratified analyses, the HR for those with a BMI ≥ 25 was 1.12 per unit (95% CI:1.05–1.19) and those with a BMI < 25 was 1.04 per unit (95% CI:0.92–1.18). MSBR is positively associated with risk for cancer mortality in a US sample, particularly among those who are overweight or obese. The utilization of standard clinical measures comprising this index may inform population cancer prevention strategies.

Allostatic overload in patients with essential hypertension

The role of psychosocial stress in the development of essential hypertension has attracted increasing attention in the last decades, even though research findings have been often inconclusive. We specifically investigated allostatic overload (AO) in hypertensive patients using a clinimetric approach. Allostatic overload was assessed by a semi-structured research interview based on clinimetric criteria in 80 consecutive outpatients with essential hypertension (46.3 % females; mean age 62.18 ± 8.59 years; age range 47-74 years) and 80 normotensive matched controls. Three clinical interviews and two self-rating questionnaires for assessing psychological distress and well-being were also administered. Cardiac variables were collected. AO was present in 26 (32.5 %) of the hypertensive patients based on clinical interviewing, and in only 6 normotensive controls (p < .001). Hypertensive patients with AO had significantly higher levels of psychological distress than those without. Further, patients with AO displayed significantly lower levels of well-being and quality of life (p < .001). A significantly greater prevalence of psychosomatic syndromes was found to be associated with the presence of AO (p < .05), whereas no significant association was detected as to psychiatric diagnoses. Significantly greater cardiovascular risk was found among hypertensive patients reporting AO compared to those without (p < .05). The results of this study support the clinical relevance of a psychological assessment of hypertensive patients, with important implications for the non-pharmacological management of hypertension.

Allostatic load in the association of depressive symptoms with incident coronary heart disease: The Jackson Heart Study

African Americans are at heightened risk for coronary heart disease (CHD), with biologic pathways poorly understood. We examined the role of allostatic load (AL) in the association of depressive symptoms with incident CHD among 2,670 African American men and women in the prospective Jackson Heart Study. Depressive symptoms were quantified using the Center for Epidemiologic Studies Depression Scale (CES-D). Incident CHD was ascertained by self-report, death certificate survey, and adjudicated medical record surveillance. Baseline AL was quantified using biologic parameters of metabolic, cardiovascular, immune, and neuroendocrine subsystems and as a combined meta-factor. Sequential models adjusted for demographic, socioeconomic, and behavioral covariates, stratified to examine differences by sex. Greater depressive symptomatology was associated with greater metabolic, cardiovascular, and immune AL (p-values≤0.036) and AL meta-factor z-scores (p = 0.007), with findings driven by observations among females. Each 1-point increase in baseline depressive symptomatology, and 1-SD increase in metabolic AL, neuroendocrine AL, and AL meta-factor z-scores was associated with 3.3%, 88%, 39%, and 130% increases in CHD risk, respectively (p-values <0.001). Neuroendocrine AL and AL meta-factor scores predicted incident CHD among males but not females in stratified analyses. Metabolic AL partially mediated the association of depressive symptoms with incident CHD (5.79% mediation, p = 0.044), a finding present among females (p = 0.016) but not males (p = 0.840). Among African American adults, we present novel findings of an association between depressive symptomatology and incident CHD, partially mediated by metabolic AL. These findings appear to be unique to females, an important consideration in the design of targeted interventions for CHD prevention.

Clinical characterization of allostatic overload

Allostatic load reflects the cumulative effects of stressful experiences in daily life and may lead to disease over time. When the cost of chronic exposure to fluctuating or heightened neural and systemic physiologic responses exceeds the coping resources of an individual, this is referred to as "toxic stress" and allostatic overload ensues. Its determination has initially relied on measurements of an interacting network of biomarkers. More recently, clinical criteria for the determination of allostatic overload, that provide information on the underlying individual experiential causes, have been developed and used in a number of investigations. These clinimetric tools can increase the number of people screened, while putting the use of biomarkers in a psychosocial context. The criteria allow the personalization of interventions to prevent or decrease the negative impact of toxic stress on health, with particular reference to lifestyle modifications and cognitive behavioral therapy.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

Association between allostatic load and health behaviours: a latent class approach

Background

Allostatic load (AL) has been characterised in many ways throughout the literature; however, its relationship to health behaviours has only been studied in limited populations. We aimed to uncover qualitative patterns of biological indicators in AL and determine if those patterns were associated with certain health behaviours.

Methods

We conducted latent class analysis using biological indicators from a multiethnic population. We fit latent class regression of class on health behaviours (smoking, poor diet, physical activity and alcohol use) to measure the association between each latent class of AL and each health behaviour.

Results

Four classes, ‘Metabolic+Cholesterol, ‘Blood Pressure’, ‘Metabolic+Blood Pressure’ and ‘Low’, were found in the sample. Latent class regression showed that physical activity and alcohol use were significantly associated with the ‘Metabolic+Blood Pressure’ class.

Conclusion

Less physical activity was required to improve AL than was previously found. Low to moderate alcohol use was beneficial for lower AL. Implications of the amount of physical activity necessary to lower AL is discussed.

Enhancing Disaster Resilience by Reducing Stress-Associated Health Impacts

Disasters are a recurring fact of life, and major incidents can have both immediate and long-lasting negative effects on the health and well-being of people, communities, and economies. A primary goal of many disaster preparedness, response, and recovery plans is to reduce the likelihood and severity of disaster impacts through increased resilience of individuals and communities. Unfortunately, most plans do not address directly major drivers of long-term disaster impacts on humans-that is, acute, chronic, and cumulative stress-and therefore do less to enhance resilience than they could. Stress has been shown to lead to or exacerbate ailments ranging from mental illness, domestic violence, substance abuse, post-traumatic stress disorders, and suicide to cardiovascular disease, respiratory problems, and other infirmities. Individuals, groups, communities, organizations, and social ties are all vulnerable to stress. Based on a targeted review of what we considered to be key literature about disasters, resilience, and disaster-associated stress effects, we recommend eight actions to improve resiliency through inclusion of stress alleviation in disaster planning: (1) Improve existing disaster behavioral and physical health programs to better address, leverage, and coordinate resources for stress reduction, relief, and treatment in disaster planning and response. (2) Emphasize pre- and post-disaster collection of relevant biomarker and other health-related data to provide a baseline of health status against which disaster impacts could be assessed, and continued monitoring of these indicators to evaluate recovery. (3) Enhance capacity of science and public health early-responders. (4) Use natural infrastructure to minimize disaster damage. (5) Expand the geography of disaster response and relief to better incorporate the displacement of affected people. (6) Utilize nature-based treatment to alleviate pre- and post-disaster stress effects on health. (7) Review disaster laws, policies, and regulations to identify opportunities to strengthen public health preparedness and responses including for stress-related impacts, better engage affected communities, and enhance provision of health services. (8) With community participation, develop and institute equitable processes pre-disaster for dealing with damage assessments, litigation, payments, and housing.

Meal-exercise challenge and physical activity reduction impact on immunity and inflammation (MERIIT trial)

BACKGROUND

The effect of a pre-exercise meal as countermeasure to exercise induced immunodepression is poorly known. Also, sedentary behavior is associated with increased cardiometabolic risk but studies on immune changes are lacking. Therefore, we aimed to assess: 1) the impact of a pre-exercise Mediterranean meal (MdM) compared with a fast-food type meal (FFM) on exercise-induced immunological changes and 2) the impact of an induced acute period of sedentary behavior on neuro-immune-endocrine status.

METHODS

/Design: This is a two steps clinical trial including: (a) randomized crossover clinical trial, comparing the effect a high-fat/low-nutrient dense meal, FFM, with an isoenergetic similar high-nutrient dense meal, MdM, in the immune response to an exercise challenge (EC) and (b) a pilot trial assessing the neuro-immune-endocrine change induced by acute decreasing by half the usual physical activity level.

RESULTS

A total of 46 participants (26 females), median aged 25 years were included. Of those 39-completed protocol, including overweight, physical active and inactive and participants with asthma. There were no differences in the EC between interventions. Dietary factors and physical activity were closely monitored during interventions and kept similar. During physical inactivity induction, 31% reached the target of 50% reduction in mean step number and 77% reached a 30% reduction.

CONCLUSION

The use of a pre-exercise meal to modulate immune response and the understanding of the immunological impact of physical inactivity might help to establish future recommendations on how to practice exercise in a safer way and to recognize the potential impact of inactivity.

Conceptual endophenotypes: A strategy to advance the impact of psychoneuroendocrinology in precision medicine

Psychobiological research has generated a tremendous amount of findings on the psychological, neuroendocrine, molecular and environmental processes that are directly relevant for mental and physical health, but have overwhelmed our capacity to meaningfully absorb, integrate, and utilize this knowledge base. Here, we reflect about suitable strategies to improve the translational success of psychoneuroendocrinological research in the era of precision medicine. Following a strategy advocated by the National Research Council and the tradition of endophenotype-based research, we advance here a new approach, termed "conceptual endophenotypes". We define the contextual and formal criteria of conceptual endophenotypes, outline criteria for filtering and selecting information, and describe how conceptual endophenotypes can be validated and implemented at the bedside. As proof-of-concept, we describe some of our findings from research that has adopted this approach in the context of stress-related disorders. We argue that conceptual endophenotypes engineer a bridge between the bench and the bedside. This approach readily lends itself to being continuously developed and implemented. Recent methodological advances, including digital phenotyping, machine learning, grassroots collaboration, and a learning healthcare system, may accelerate the development and implementation of this conceptual endophenotype approach.

Assessment of cumulative health risk in the World Trade Center general responder cohort

BACKGROUND

Multiple comorbidities have been reported among rescue/recovery workers responding to the 9/11/2001 WTC disaster. In this study, we developed an index that quantifies the cumulative physiological burden of comorbidities and predicts life expectancy in this cohort.

METHODS

A machine learning approach (gradient boosting) was used to model the relationship between mortality and several clinical parameters (laboratory test results, blood pressure, pulmonary function measures). This model was used to construct a risk index, which was validated by assessing its association with a number of health outcomes within the WTC general responder cohort.

RESULTS

The risk index showed significant associations with mortality, self-assessed physical health, and onset of multiple chronic conditions, particularly COPD, hypertension, asthma, and sleep apnea.

CONCLUSION

As an aggregate of several clinical parameters, this index serves as a cumulative measure of physiological dysregulation and could be utilized as a prognostic indicator of life expectancy and morbidity risk.

Allostatic breakdown of cascading homeostat systems: A computational approach

Homeostasis posits that physiological systems compensate setpoint deviations in an attempt to maintain a state of internal constancy. Allostasis, on the other hand, suggests that physiological regulation is more appropriately described by predictive modulatory actions that, by adjusting setpoints, anticipate and react to changes in internal and external demand. In other words, “maintaining stability through change.” The allostatic perspective enabled the rationalization of predictive and reactive homeostasis. While the latter reflects external perturbations, the former refers to systemic adaptation in response to anticipated changes − not necessarily related to unexpected external disturbances. Therefore, the concept of allostasis accounts also for adaptation to circadian variations (seasonal, circannual or other predictive variability) and interprets the system’s adaptation of its setpoints not as reactive/subnormal adjustments, but rather as a proper response. Therefore, systemic entrainment to periodic demands is handled by predicting and implementing setpoint changes. Given the important role of circadian variability and regulation in maintaining health, and the loss of circadian entrainment as a predisposing factor and sequel of stress, we elaborate on an allostasis model which demonstrates the ability of the systems to adapt to circadian demands and quantifies the deteriorative natural wear and tear of a system constantly adapting, i.e. the irreversible damage and its consequences on system function and overall survival. While developing a system of cascaded nature, we demonstrate the importance of phase coordination and the implications of maintaining proper phase relations. The disruption of these relations is a hallmark of circadian disruption, a predisposing factor to increased vulnerability and/or a sequel to chronic stress.

Social status and biological dysregulation: the "status syndrome" and allostatic load

Data from a national sample of 1255 adults who were part of the MIDUS (Mid-life in the U.S.) follow-up study and agreed to participate in a clinic-based in-depth assessment of their health status were used to test the hypothesis that, quite part from income or educational status, perceptions of lower achieved rank relative to others and of relative inequality in key life domains would be associated with greater evidence of biological health risks (i.e., higher allostatic load). Results indicate that over a variety of status indices (including, for example, the person's sense of control, placement in the community rank hierarchy, perception of inequality in the workplace) a syndrome of perceived relative deprivation is associated with higher levels of biological dysregulation. The evidence is interpreted in light of the well-established associations between lower socio-economic status and various clinically identified health morbidities. The present evidence serves, in effect, both as a part of the explanation of how socio-economic disparities produce downstream morbidity, and as an early warning system regarding the ultimate health effects of currently increasing status inequalities.